1. Field of the Invention
This invention relates broadly to a means and method for increasing the rate of fluid flow along a flow path downstream of a curved flow passage, and more specifically relates to internal-combustion engines, and to a means and method for increasing the rate of air flow into the combustion chamber of such an engine to increase the power output of the engine.
2. DESCRIPTION OF THE RELATED ART
In the development of internal-combustion engines, continuing effort has been focused on improving such engines to increase their power output.
Particular attention has been directed to such improvements in the field of internal-combustion engines for compact cars, motorcycles, and internal-combustion engine-powered consumer products, e.g., portable generators, paint sprayers, lawn mowers, edgers, and the like. In these applications, size and weight considerations are important, often critical, to the commercial viability and consumer acceptance of the product in which the internal-combustion engine is employed.
In addition to providing advantages of size reduction of the engine in the aforementioned applications, improvement of the power output of the internal-combustion engine likewise provides the benefit of improved fuel consumption characteristics for the engine. Such increases in combustion efficiency of the engine mean that less fuel is required for a given duration of operation, or alternatively, a longer duration of operation can be achieved on the same amount of fuel.
Among the aforementioned internal combustion engine applications, particularly significant effort has been expended to achieving enhanced power output in highperformance motorcycle engines, where considerations of size, weight, and horsepower are paramount. The U.S. patents hereinafter described relate to internal combustion engine improvements particularly applicable to motorcycles.
U.S. Pat. No. 4,470,391 to T. Ishida discloses an air-fuel mixture intake construction for an internal-combustion engine, utilizing a so-called induction passage. One end of such passage opens into a secondary intake passage, upstream of a secondary throttle valve therein, and the other end opens immediately upstream of the intake valve for the combustion chamber. The secondary intake system supplements the primary intake system, and furnishes air-fuel mixture under medium and high engine loads.
In operation, the induction passage ejects air and/or air-fuel mixture into the combustion chamber to create swirling flows therein. This is said to promote fuel combustion in the combustion chamber.
The patent also discloses the use of plural induction passages for multi-cylinder engines, similiarly constructed with their distal ends opening immediately upstream of the intake valves. The induction passages in the disclosed construction are connected at their other ends (opposite the distal ends) to a common passage which communicates with primary intake passages immediately downstream of a primary throttle valve and which also communicates with a slow fuel supply passage in the secondary intake passage. The induction passages comprise pipes opening into the secondary intake passages immediately upstream of the secondary throttle valves.
Although this patent discloses (at column 6, lines 26-30) that a high vacuum is developed at the induction pipe on the intake stroke during the idling mode of operation, such vacuum conditions appear localized in the intake passage so as to cause air or lean air-fuel mixture to flow through the induction passage. As stated in column 6, at lines 61-68, the "vacuum developed at the induction pipe causes air or a lean air-fuel mixture to flow . . . into the . . . passageway 84, and the pipe 85 [the induction passageway], from which the air or air-fuel mixture is ejected rapidly into the combustion chamber 2 circumferentially thereof in the direction in which the air-fuel mixtures are fed from the intake ports 3, 4."
U.S. Pat. No. 4,488,519 to H. Kishida discloses an internal combustion engine configuration in which a check valve is deployed in the intake passage upsteam of the combustion chamber. The check valve prevents reverse flow from the chamber through the intake passage, and a plenum chamber communicates with the intake passage downstream of the check valve. In this construction, the plenum chamber is provided with flow through a relatively small pipe having an inlet disposed immediately adjacent to the intake valve 23 and downstream of the reed-type check valve 24 (Column 3, line 1-5).
Column 3, lines 33-38 of this patent disclose that when the "intake valve 23 closes, there will be a negative pressure existent in the plenum chamber 26 which tends to cause a continued flow through the induction passage and which will tend to prevent the reed-type check valve 24 from completely closing, particularly at higher speeds."
U.S. Pat. No. 4,530,325 to Y. Namba, et al. discloses what is termed a suction system for an internal-combustion engine. The term "suction" used in this context, however, refers to intake flow of air-fuel mixture into the combustion chamber.
This is apparent from the disclosure in the patent at column 2, lines 43-54, where it is disclosed that an injection nozzle pipe forms the outlet end portion of the sub-suction path in the engine. The pipe has a nozzle portion with reduced diameter at its tip such that it is opened immediately upstream of the suction valve (intake valve). This passage specifically states that the "injection nozzle pipe 23 is directed substantially in the tangential direction of the wall of the cylinder 1 so that a swirl of the suction gases is generated around the axis of said cylinder 1 in the combustion chamber."
Further, in describing the operation of the engine comprising the disclosed improvement, this patent at column 3, lines 31-40 discloses that in such engine, "during the suction stroke having the suction valve 10 opened, the combustion chamber 4 is supplied with an air-fuel mixture from the main suction path 5, whereas a gas is injected from the sub-suction path 22 into the combustion chamber 4. By the injection of the gas from the sub-suction path 22, the mixture sucked into the combustion chamber 4 is swirled around the axis of the cylinder 1 so that the burning velocity is accelerated."
As is well known, the amount of power that an internal combustion engine is capable of developing is directly related to the amount of air or air-fuel mixture that can pass through the intake passage of the engine during the inlet cycle. Thus, if a suitable means or method is found to increase this flow of air or air-fuel mixture into the combustion chamber, more power output will be obtained.
For many years, one of the standard approaches to increasing air flow in intake passages of internal combustion engines has involved "porting" or otherwise reshaping, recontouring, or polishing the intake ports of the internal combustion engine, including the valve seat area. While major air flow gains are achievable by such approaches, they are generally expensive, time-consuming, and ill-suited to mass production.
Accordingly, there is a coninuing need in the internal combustion engine art for improvements in engine construction and operation which will increase the rate of air and air-fuel mixture flow into the combustion chamber, to thereby realize improvements in power output of the engine.
It therefore is an object of the invention to provide a means and method for effecting improvement in the rate of air flow and flow of air-fuel mixture into the combustion chamber of an internal combustion engine, to increase its power output.
It is a further object of the invention to provide a means and method of the type described above, which is readily implemented in the retrofitting of existing internal combustion engines, and which is well suited for the construction and operation of new engines fabricated by mass production techniques.
It is a still further object of the invention to provide a means and method for increasing fluid flow rate in a flow path downstream of a curved portion of the path.
Other objects and advantages of the invention will be more fully apparent from the ensuing disclosure and appended claims.